From his vantage point in a car a few dozen feet in front of a 20,000-pound big rig barreling along a Florida highway without anyone behind its wheel, Stefan Seltz-Axmacher felt like everything was going according to plan.

As the founder of self-driving-truck startup Starsky Robotics, he had spent more than two years building to this moment, when a truck with no human sitting in the front seat, no safety driver waiting in the sleeper berth, no human anywhere on board, would trundle along a public road. Now, watching the first two miles of the groundbreaking journey from a lead car riding in front of the tractor-trailer, he confessed that it all felt routine. Maybe even, like the reality of so much of current autonomous-vehicle testing, boring.

And that’s precisely when the truck inexplicably slowed and stopped in the middle of the road.

“I’m thinking, ‘This is not planned,’ ” Seltz-Axmacher said. “And so we get out and turn off the engine and start investigating.”

Starsky Robotics engineers tested and developed the autonomous-driving system, which has been installed in the Freightliner Cascadia for more than a year, and had spent a full week conducting dry runs on the stretch of County Road 833 in southern Florida, just north of the Everglades. They had plotted every conceivable contingency and every imaginable edge-case scenario.

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“Of all the different flaws that could have happened,all those things we tested and expected, we never tested shutting down the power to the building.”

– Stefan Seltz-Axmacher, Starsky Robotics

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In doing so, they illustrated one of the more vexing aspects of automated driving not just for themselves, but for every company that is developing self-driving technology: For all the tens of thousands of scenarios gathered through millions of miles of testing, it’s the unforeseen outlier that looms as the one of the most complicated challenges in deploying a self-driving vehicle.

On this highly anticipated mid-February afternoon, during the most important test to date, that outlier was the improbable circumstance that the building housing the company’s remote operations team in Plantation, Florida, lost power. When the truck lost its signal from the teleoperations center, dozens of miles away from the test road, it immediately went into a safe mode and came to a gradual stop in its lane of travel.

Far from what was expected, but for Seltz-Axmacher and his team, it was reassuring to see the truck proved it could handle the unexpected.

“Of all the different flaws that could have happened, all those things we tested and expected, we never tested shutting down the power to the building,” he said. “But by having this safety architecture in place, you are able to be confident that if a failure happens, even weird failures that have never happened to us before, we will catch them. If we catch them, we will come to a stop.”

Taking Driverless to New Levels

Once the issue was identified and power restored, the company continued the fully driverless journey and completed five more miles of testing along the intended route. One day later, Starsky Robotics completed the entire seven-mile stretch along County Road 833 without a human aboard, and without incident.

Among companies developing self-driving-truck technology, it’s believed that this was the first fully driverless test on a public road with no human safety driver aboard. In October 2016, Otto, a self-driving truck subsidiary of Uber, conducted a 120-mile test along Interstate 25 between Fort Collins and Colorado Springs, Colorado, but it had a human safety driver monitoring the test from the bunk. Since then, Otto has been folded into a unit of the company now known as Uber Freight.

Both tests were highly structured, in that local officials and law enforcement had shut down the roads temporarily or worked to separate the test trucks from regular traffic. But for Seltz-Axmacher, last month’s test, conducted at a maximum speed of 35 miles per hour, was another milepost in the race to deploy autonomous trucks.

“It’s a huge deal for us, and a really big sign of how serious we are,” he said. “The other teams have not done that. We can test all day long with someone behind the wheel and everyone could just focus on testing reliability and growing a feature set of what their system can do. They can make each thing reliable enough that it doesn’t fail often—but if it does, it can be controlled by the person behind the wheel.

“But the problem we’re trying to solve is the person in the truck. It’s time to do unmanned testing.”

Eleven months ago, Starsky Robotics started using self-driving trucks to haul commercial freight, and it fine-tuned its system in truck yards, hauling everything from 5000 pounds of milk crates to 40,000 pounds of tile. Last fall, a truck hauled bottled water to Florida residents affected by Hurricane Irma. It traveled a 68-mile stretch of Interstate 75 between Fort Myers and Miami under control of its self-driving system without requiring any intervention from its human safety driver.

Starsky’s steady progression has brought the notice of venture-capital firms. On Thursday, the company announced that Shasta Ventures has led a funding round that has collectively raised $16.5 million. Other investors include Y Combinator, Trucks Venture Capital, Fifty Years, and 9Point Ventures.

Over the remainder of 2018, Seltz-Axmacher said, the company intends to up the frequency of its unmanned testing runs, which will include freight hauls at some point. Florida is the current location for testing, but Starsky likely will expand to other states by year’s end.

Remote Connections Grow in Importance

Although based in the Bay Area, the company cannot test in its home state because California prohibits automated testing of vehicles that weigh 10,001 pounds or more. But the California Department of Motor Vehicles and others may nonetheless want to pay close attention to the company and its experience with teleoperations, a slice of autonomous operations that’s increasing in importance.

In late February, the California DMV finalized revised statewide regulations that govern autonomous testing which permit the testing of fully driverless vehicles with no safety drivers aboard, as long as the cars can be controlled through remote operations.

In Starsky’s case, cameras installed in the cab and around the truck give remote operators a bird’s-eye view around the truck. These operators can take control and remotely guide the truck through situations that its self-driving systems can’t comprehend on their own. For example, one of the company’s trucks approached an intersection where a fire truck was parked near the shoulder of the road and a firefighter was standing in the middle of the road directing traffic. Although a safety driver was aboard the test truck, remote operators guided the truck through the intersection.

“If a vehicle in front of the truck slams on its brakes, that’s a safety-critical decision that’s handled by the truck itself,” Seltz-Axmacher said. “Decisions where teleoperations are involved take five to 15 seconds to make; they’re not safety critical. It’s ‘I’m stuck behind a slow-moving vehicle. Should I pass or not?’ ” Those kinds of decisions are easy to make in the office.”

And when the office unexpectedly closes down, the trucks make the safest decision of all: simply stop.